Field of the Invention
The invention concerns a placement station for placing flat items and feeding them to a singularization station, used in an item processing system, for example as a station of a mail line of a franking system.
Description of the Prior Art
The mail line of a franking system is composed of a number of successively arranged individual mail item processing stations. A placement station is installed in the mail-item flow upstream a singularization station, i.e. in many cases at the beginning of a mail line and serves to place individual or stacked mail items on the singularization station that singularizes the stack. When there is used an upstream enveloping station which successively throws individual enveloped letters on the placement deck of the placement station, said enveloping station will form the beginning of the mail line of course.
A stack of mail items of the same format or of different formats (mixed mail items), that has been put on an alignment wall of the placement station will be singularized in the mail line by means of a singularization station directly following downstream in transport direction because further subsequent mail item processing stations, such as e.g. a dynamic balance, require individually fed mail items. The placement station is intended for use in connection with further stations of the item processing system that follow downstream, for example in connection with franking or addressing machines and other mail item processing units.
In the United States, the “Letter” standard sizes must be processed, such as Letter 8½ inch×11 inch (21.59 cm×27.94 cm), Letter 8½ inch×14 inch (21.59 cm×35.56 cm), Letter 14⅞ inch×11.69 inch (37.8 cm×29.69 cm). In particular in Germany, the sizes B4 (25.0 cm×35.3 cm), B5 (17.6 cm×25.0 cm), B6 (12.5 cm×17.6 cm) and C4 (22.9 cm×32.4 cm), C5 (16.2 cm×22.9 cm), C6 (11.4 cm×16.2 cm) are usual. The sizes of the German paper formats were fixed in the year of 1922 already by Deutsches Institut far Normung (DIN) in the DIN Standard DIN 476.
When speaking of a stack below, this shall mean letter stacks, card stacks and other stacks of mail items that can be singularized, while other stacked flat items shall not be excluded.
Known mail processing devices feed the lowermost mail item of a mail item stack to an alignment wall by means of driven rollers. From U.S. Pat. No. 4,973,037, there is already known a feeding station for a mail handling machine designed for the handling of mixed mail (filled envelopes with open or closed envelope flap) at high speed. The deck is called stack plate. The feeding station is equipped with a device for transversal movement of a side wall relative to the stack plate and with transport devices in a stack magazine area. Part of the transport devices is located below the stack plate. The side wall serves as alignment surface against which the flap edges of envelopes can be positioned. The transport means of the feeding station are eccentrically designed loosening rollers with different friction coefficients that, during a rotation of the loosening roller, alternatingly come up over and go down below a placement deck so that a lowermost flat item of a stack of flat items is intermittently contacted. The friction on the rollers while the flat items are intermittently contacted and the force needed for lifting the stack are very high in case of high and heavy stacks. A plurality of roller groups of loosening rollers is driven by a first motor that must deliver the required force. The plurality of roller groups of loosening rollers is arranged in a rack that can be periodically moved back and forth within a small angular range by means of a second motor and a control disk. The use of such loosening rollers with a force periodically acting on a stack, however, causes an uneven run with an increased noise level. The coupling of undesired oscillation considerably interferes with a dynamic weight measurement in a franking system.
There are already provided means for transporting the mail items in downstream direction as well as also in direction to the alignment wall as well as for loosening up the mail items (open or closed filled envelopes) of a stack so that they can slide more easily over one another. There was also proposed multiple inclining of the mail item stack plate in the stack magazine area in order to use gravity for aligning the mail items. By a multiple inclining of the mail item stack plate in the stack magazine area, the envelope may get jammed when passing into the feeding sector in a horizontal position, in particular with an open envelope flap. Due to the small angular sector, an alignment of the mail items is only possible to a limited extent.
According to EP 1 533 260 B1, a jogging device is proposed for feeding mail items (letters) to a singularization station. On the entire width of the sluice of the above-mentioned singularization station, there is provided an outer strip with a movable sliding rail at the end of which a jogging flap is arranged. After placing a stack with letters lying on their side, the letters are moved by means of the jogging flap in longitudinal direction against a reference wall and thereby are loosened up by means of the jogging flap and thus are aligned, i.e. put in the correct position before a subsequent singularization and printing. The jogging flap forms a laterally shiftable stop with a sliding guide that must be adjusted to the letter width and can be locked in this position by means of a friction brake. The jogging flap acts directly on the lateral positioning of mail items. In addition, there is also provided a second sliding guide that allows a resilient overstroke by means of a spring so as to avoid jamming of the letters. However, only letters having the same format can be aligned with this device.
A feeding device according to EP 1 958 902 B1 is provided with an improved transport device having a plurality of drive members with the special feature that they consist of a cylindrical wheel with teeth provided on its circumference in a gear-wheel-like manner between which axles for small non-driven independently rotatable rollers are arranged. An alignment is possible by manually moving a mail item or a stack of mail items on an alignment wall.
EP 1 510 480 B1 refers to an alignment device of a mail handling system having jogging and alignment devices with a plurality of retractable elements that extend through openings in a horizontal plate the distance of which to an alignment wall (reference wall) can be adjusted according to the format of the mail items in order to guide the mail items in a forced manner, which shall contribute to prevent an inclining of the mail items.
In the above-mentioned European patents EP 1 533 260 B1, EP 1 958 902 B1, and EP 1 510 480 B1, the functions of placement station and singularization station were combined in a single feeding and printing station. There were also used driven transport rollers, but they cannot be adjusted in their angular position in relation to the transport direction. The correct alignment of the mail items is realized by means of sliding elements and jogging elements of various kinds.
These item processing appliances are very noisy during operation and also susceptible to failure in the processing of a stack of mail items. While the alignment of individual mail items is unproblematic, there may already occur problems in the alignment of a stack of mail items of the same format when there are differences in sizes. Major problems occur in the alignment of a stack of mixed mail containing mail items of different thicknesses and different dimensions.
In the field of franking machines, it is already known to transport a singularized mail item from a stack in transport direction downstream the mail-item flow and printing a franking print on it during the transport. In the Centormail® franking machine of the applicant, there is already transported mixed mail standing on the edge using a transport belt, wherein the mail items are automatically aligned on the edge by the effect of gravity.
In the field of franking machines, there are also known solutions that transport a mail item lying on a side in transport direction downstream the mail-item flow, like for example the PostBase® franking machine of the applicant. To this franking machine, an automatic feeding station can be added on the mail-item entrance side. The franking system formed this way, however, is not suitable for mixed mail, but only for mail items of the same format.
In the German utility model DE 20 2011 107 379 U1 that is equivalent to U.S. Pat. No. 8,702,090 B2, there was already proposed a modular placement device for a feeding station. The feeding station follows, in the direction downstream the mail-item flow, the placement station that is designed as a module for merely manual operation without own drive technology the placement deck of which can be put up in a ramp-like manner when required. Due to the ramp put up, the effect of gravity is used in the feeding of mail items. But the mail items are not aligned by the effect of gravity. There is rather provided a slider by means of which a stack is manually pressed on a guide plate of the placement station that serves as alignment wall. This way only differently thick mail items of the same format can be reliably processed up to a rate of 65 mail items of the DIN format C6 or C6-long per minute. Thus, it can be ensured by means of the slider that all mail items of a mixed-mail stack lie on the alignment wall with their side edge. Edge alignment becomes problematic when the mail items transported in a position lying on their side shall be aligned on an alignment, placement or guide wall without the contribution of gravity. To be on the safe side, a stack of mail items is therefore manually aligned on one edge of the stack and then is placed. In practice, there do also occur deviations in the format of mail items, which may lead to undesired failures in operation.
In the following, the term mixed mail shall mean differently thick, flat mail items of a stack mainly of the same format that, despite a tolerance of up to +/−20 mm, must be processed by the mail item processing stations.
It is a problem to develop a placement station for placing an individual flat item as well as also a stack of flat items and feeding them to a singularization station that allows for a higher throughput of flat items, wherein the flat items are transported lying on their side and the above-mentioned disadvantages of the prior art do not occur. The placement station shall be designed as a separate module for edge alignment of flat items with own drive equipment to be arranged in a position upstream a singularization station. The correct alignment of a stack of flat items (mail items) shall be realized without sliding elements and jogging elements of various kinds as they are usual for flat items of the same format. It is known that, with a higher throughput, the error rate in the singularization of a flat item from a stack increases, too. When drawing the respective lowermost flat item off from an aligned stack, the other flat items remaining in the stack may be inadvertently put into an unaligned position so that the alignment edge of some of the flat items may reach a distance of 3 to 5 mm from the alignment wall. Then, the stack is not correctly aligned anymore. It is intended that the stack may contain flat items of different thickness and with format deviations in length and width while, nevertheless, the placement edge of the respective lowermost one of the flat items of the stack shall be correctly guided to the alignment wall and aligned. In particular, the placement station together with the singularization station shall allow for a higher throughput of up to 100 mail items of the DIN format C6 or C6-long per minute.
In such a placement station, the error rate may further increase due to such flat items the surfaces of which have a very different friction coefficient in case of contact with the surfaces of other items or with the surfaces of the transport elements, in particular also in case of items that are not mail items. By the internal drive technology of the module, there may be exerted on the flat items, selectable via traction, other forces than by the effect of gravity so that squeezing or crumpling of a flat item, such as e.g. a letter envelope, on the alignment wall becomes more probable when the drive equipment shall not only feed the flat items in transport direction to the feeding station immediately following downstream, but also align them on the alignment wall. Therefore, it is a further problem to reduce the error rate and increase the singularization reliability by a correct alignment of the stack. The flat items lying directly on the placement deck, i.e. the lowermost, non-aligned flat items of a stack shall be automatically aligned on the alignment wall of the placement station without the occurrence of any squeezing or crumpling of a flat item on the alignment wall.
It is intended that the flat items within a stack may have different dimensions (thickness and dimension deviations). The placement station should be suitable for mail items, but also for other stackable items which have format deviations of up to 20% in length and width.